Contradictory diet advice making healthy eating even harder – 台北時報

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While some nutrition experts preach the gospel of vegetables, others pray at the altar of meat, but what really makes a difference might be unique to each person

  • By F.D. Flam / Bloomberg Opinion

’Tis the season of wavering New Year’s resolutions, and 2024 might be an especially hard year to keep to a new diet because there are so many contradictory claims —and so little left on the menu that is not being vilified by someone with initials after their name.

Mainstream experts are still warning against eating meat, cheese, sugar and the ill-defined group known as ultra-processed foods. Now people are saying to avoid tomatoes, peppers and eggplant, and even one theory says that people are poisoning themselves with spinach.

On everyone’s good list? Cauliflower. At least, for now.

Illustration: Yusha

Spinach and kale are on the bad list of Sally K. Norton, who has a degree in public health, but has strayed from the mainstream by advising against foods high in substances called oxalates. Her bad list also includes beans, grains, almonds, potatoes, beets and chocolate — what she calls “toxic superfoods.”

Oxalates are real compounds and there is some scientific debate about their contribution to kidney stones. Norton’s hypothesis is that oxalates caused her chronic pain and might also cause nervous system problems, premature aging, hearing loss and eye floaters.

Meanwhile, heart surgeon Steven Gundry says that people might be sickened by a different group of plants — ones high in lectins, which are part of plants’ defense systems. He blames lectins for a host of problems from bad digestion to autoimmune disease to weight gain. In his diet, spinach and greens are acceptable, but not tomatoes, peppers, seeds, beans or whole grains.

The Office for Science and Society at McGill University has a nice write-up puncturing the oxalate theory. Chemist Joe Schwarcz, who heads the office, debunks the widespread dangers of lectins in a chapter in his diet-myth-busting book A Grain of Salt.

Schwarcz said that some plants contain minute traces of compounds that are toxic at vastly higher doses.

It makes no sense to talk about something as toxic without considering the amount, he said, adding that the preponderance of evidence suggests that the more fruits, vegetables and whole grains a person eats — and the less fat — the better off they are.

Even age-old assumptions about fats are now contested.

Olive oil is considered a good fat, and many now say that saturated fats found in meat and dairy are not the dietary villains they have been made out to be. Some recent studies suggest that those who ate full-fat dairy were healthier than those who went for low-fat or nonfat options.

Journalist Gary Taubes, author of Rethinking Diabetes, has been a longtime critic of the mainstream advice to eat a low-fat diet.

That recommendation is based not on rigorous science, but observations comparing people in different countries, he said.

Those kinds of studies cannot easily untangle which health differences might be due to socioeconomic factors and other variables.

Another reason for some of the conflicting evidence over which foods are healthy is that many studies simply ask study subjects to remember what they ate — that does not always make it clear which foods make a difference.

The studies aimed at finding long-term benefits from a particular diet are not all that rigorous. One of the most widely publicized studies of longevity — the “blue zones” — examined the diet and lifestyle of people in five regions of the world with purportedly unusual longevity. It is an intriguing observation and made for an entertaining Netflix series, but it is impossible to pin longevity in these regions on diet, let alone any particular kind of food.

However, out of all the contradictory claims, there is one area of agreement: Diet influences health, and it is possible to benefit from experimenting on yourself. Any individual might have food sensitivities that differ from the population at large.

A diet that makes you feel energetic and helps you achieve a healthy weight might indeed be better for you, as an individual, than what has been associated with longevity in large populations. Some people feel better avoiding gluten even if they do not have celiac disease, and others might feel better skipping dairy products. Maybe a few people are sensitive to lectins or oxalates and benefit from avoiding them. It would be easier to stick with any diet plan if it is giving you short-term benefits.

So instead of New Year’s resolutions, we could have New Year’s experiments. If a change does not make you feel better, you can still consider it a lesson learned — and there is always cauliflower.

F.D. Flam is a Bloomberg Opinion columnist covering science. She is host of the Follow the Science podcast. This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

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